Force controlling system

ABSTRACT

In a force controlling system, a movable member fixed to an elastic member applies a force to an object in correspondence with a force reference signal. At this time, an additional force is applied via a driver to the movable member by the positive feedback of the displacement of the elastic member to the driver, so that the reactive force due to the displacement of the elastic member is counteracted by the additional force. As a result, the movable memer applies only a force in correspondence to the force reference signal to the object.

"This is a continuation of co-pending application Ser. No. 675,867 filedon Nov. 28, 1984, now abandoned."

BACKGROUND OF THE INVENTION

The present invention relates to a system for controlling a force andparticularly a very small force. Such a system is used in a grippingapparatus of a robot, a tactile apparatus, and the like.

Recently, the remarkable progress in factory automation (FA) or flexiblemanufacturing systems (FMS) has caused a large-scale integration ofrobots into the manufacturing processes. However, since conventionalposition control type robots operate regardless of their environment,such robots cannot be applied to semiconductor processes requiring finestructure operations, assembling processes for magnetic heads,inspection processes for soft food or soft materials, and the like.Thus, there is a demand for a system for controlling a very small forcein robots, free of the above disadvantages.

For example, in the prior art, in the case of controlling a grippingforce, a pressure sensor is provided in a gripping portion of a hand,thereby controlling the gripping force with an open angle of the hand.In this case, it is necessary to switch between position control andforce control modes at a certain timing; however, it is difficult tocontrol such a timing. Also, it is nearly impossible to accuratelycontrol a very small force, since the hand itself has friction. Inaddition, since a difference in gain between the position control modeand the force control mode is affected by the speed of motion of thehand, vibration and collision occur at a timing when the hand comes incontact with an object. Thus, it is almost impossible to control agripping force within a small range. Further, one control circuit andone sensor are required for each of the position control mode and theforce control mode, thus increasing the manufacturing cost.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system forcontrolling a force, particularly, a very small force.

According to the present invention, a movable member fixed to an elasticmember applies a force, in correspondence with a force informationsignal, to an object. At this time, an additional force is applied via adriving means to the movable member by the positive feedback of thedisplacement of the elastic member to the driving means, so that thereactive force due to the displacement of the elastic member iscounteracted by the additional force. As a result, the movable memberapplies only the force, corresponding to the force information signal,to the object. Thus, if this force information signal indicates a verysmall force, only such a very small force is applied to the object.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from thedescription as set forth below with reference to the accompanyingdrawings, wherein:

FIG. 1 is a cross-sectional view of a robot hand according to a firstembodiment of the present invention;

FIG. 2 is a control block diagram of the robot hand of FIG. 1;

FIG. 3 is a circuit diagram of the control circuit of FIG. 1;

FIG. 4 is an exploded, perspective view of another robot hand accordingto the present invention;

FIG. 5 is an exploded, perspective view explaining the assembling of therobot hand of FIG. 4;

FIG. 6 is a perspective view of a robot hand according to a secondembodiment of the present invention;

FIG. 7 is a perspective view of a robot hand according to a thirdembodiment of the present invention;

FIG. 8 is a perspective view of a modification of FIG. 7;

FIGS. 9 and 10 are control system block diagrams explaining theoperation of the robot hand of FIGS. 7 and 8;

FIG. 11 is an elevational view of another modification of FIG. 7;

FIG. 12 is a side view of FIG. 11;

FIG. 13 is a cross-sectional view taken along the lines A-A' of FIG. 11;

FIG. 14 is an elevational view similar to FIG. 11;

FIG. 15 is a side view of FIG. 14;

FIGS. 16A and 16B are diagrams of still another modification of therobot hand of FIG. 7;

FIG. 17 is an elevational view of a still further modification of therobot hand of FIG. 7;

FIG. 18 is a cross-sectional view of the feed screw of FIG. 17;

FIG. 19 is an elevational view of a robot hand according to a fourthembodiment of the present invention;

FIG. 20 is a perspective view of a tactile apparatus according to afifth embodiment of the present invention;

FIGS. 21 and 22 are cross-sectional views of the apparatus of FIG. 20;

FIG. 23 is a control system block diagram explaining the operation ofthe apparatus of FIG. 20;

FIG. 24 is a perspective view of a robot system according to a sixthembodiment of the present invention; and

FIG. 25 is a partial perspective view of the two-dimensional forcegenerating apparatus of FIG. 24.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, which illustrates a first embodiment of the presentinvention, reference numeral 1 designates a robot arm on which a handbase 2 is mounted. The hand base 2 has two finger portions 3-1 and 3-2.In this case, the finger portions 3-1 is a rigid member, i.e., astationary member, while the finger portion 3-2 is supported by twoparallel-plate springs 4-1 and 4-2 which are linked between the portion3-2 and the hand base 2. That is, the finger portion 3-2 serves as amovable member. Each of the parallel-plate springs 4-1 and 4-2 generatesa reactive force when the finger portion 3-2 is shifted as indicated byarrows from a balance point. Fixed to the inside of the parallel-platesprings 4-1 and 4-2 are strain gauges 5-1 and 5-2, respectively, fordetecting the displacement of the parallel-plate springs 4-1 and 4-2.The output signals of the strain gauges 5-1 and 5-2 are supplied to acontrol circuit 6 which receives a force information signalγ.

The control circuit 6 controls a voice coil motor 7 which is a kind oflinear motor. The voice coil motor 7 is comprised of a yoke 72 havingpermanent magnets 72-1 and 72-2, and a bobbin 73 on which a coil 74 iswound. The yoke 72 is fixed to the hand base 2, while the bobbin 73 isfixed to the finger portion 3-2.

Thus, the control circuit 6 controls the voice coil motor 7 to drive thefinger portion 3-2, thereby gripping an object 8 with the two fingerportions 3-1 and 3-2. Reference numeral 9 designates a stopper forstopping the finger portion 3-2 when the portion moves to the outside.

Note that the parallel-plate springs 4-1 and 4-2 have low shear moduliin one direction and high shear moduli in other directions, andaccordingly, the parallel-plate springs 4-1 and 4-2 serve as aneffectively frictionless one-way guide.

In FIG. 1, the gripping force of the finger portions 3-1 and 3-2 iscontrolled by the force generated by the voice coil motor 7, not by theopening angle of the finger portions 3-1 and 3-2. In addition, theoutput signals of the strain gauges 5-1 and 5-2 are fed back positivelyto the voice coil motor 7 via the control circuit 6.

The control block diagram of the robot hand of FIG. 1 is illustrated inFIG. 2. In FIG. 2, reference S designates a Laplace operator, O_(c)designates an open-loop gain of the power amplifier (not shown) of thecontrol circuit 6, B designates a space magnetic flux density of thevoice coil motor 7, and l designates the length of the coil 74.Therefore, Bl is the force constant of the voice coil motor 7. Theoutput V₁ (S) of the power amplifier of the control circuit 6 is appliedpositively to the coil 74, and in addition, the counterelectromotiveforce V₂ (S) of the voice coil motor 7 obtained by multiplying the speedX(S) by the force constant Bl is applied negatively to the coil 74. Thatis, V(S)=(V₁ (S)-V₂ (S)) is applied to the coil 74.

The current I(S) flowing through the coil 74 is obtained by dividingV(S) by the impedance (LS+R) of the voice coil motor 7, where L and Rare the inductance and resistance thereof, respectively. The force F₁(S) generated by the voice coil motor 7 is obtained by multiplying thecurrent I(S) by the force constant Bl of the voice coil motor 7. Thisforce F₁ (S) is applied positively to the movable portion, i.e., thefinger portion 3-2. Also, the reactive force F₂ (S) of theparallel-plate springs 4-1 and 4-2, which is kX(S) (k: stiffness of thesprings 4-1 and 4-2, X(S): displacement of the finger portion 3-2), isapplied negatively to the finger portion 3-2. That is, the forceF(S)(=F₁ (S)-F₂ (S)) is applied to the finger portion 3-2.

The speed X(S) is obtained by dividing F(S) by the mechanical impedance(MS+D) of the finger portion 3-2, where M and D are the mass and dampingcoefficient thereof, respectively.

Note that the force F₁ (S) generated by the voice coil motor 7 has agood linear characteristic regarding the current I(S), since the spacemagnetic flux density B of the voice coil motor 7 is definite regardlessof the displacement thereof. As a result, the calculated force issubstantially consistent with the measurement thereof.

In the control circuit 6 of FIG. 2, the displacement X(S) of the fingerportion 3-2 is fed back positively thereto voice coil motor 7, while thedisplacement speed X(S) of the finger portion 3-2 and the current of thevoice coil motor 7 are fed back negatively thereto and P_(c), V_(c), andI_(c) are feedback gains of the X(S), the displacement speed X(S), andthe current I(S), respectively.

The characteristics of the voice coil motor 7 are represented by##EQU1##

In addition, the transfer function of the force reference signal R(S) tothe displacement X(S) of the finger portion 3-2 is represented by##EQU2## Therefore, the damping coefficient of the entire system isrepresented by ##EQU3## Also the stiffness of the entire system isrepresented by ##EQU4##

Therefore, where the force reference signal R(S) is changed in step, thesteady-state position error of the displacement X(S) is ##EQU5## Sincethe gain O_(c) of the power amplifier is generally very large, forexample, from 80 dB to 100 dB, and kR/Bl is nearly zero, thesteady-state position error is nearly zero. This is preferable forposition control type robots, but is not preferable for force controltype robots because, if the width of an object is not accurate, thevoice coil motor 7 serves as a spring having a stiffness as shown informula (6) due to the error of a width indication value, therebygenerating a large force. Thus, it is impossible to precisely control aforce such as a gripping force.

In the present invention, the term (KIc/Bl-P_(c))O_(c) in formula (6) isas low as possible while retaining the entire system in a stable state,thereby preventing a force due to the position error from beinggenerated. This is possible, since the displacement X(S) is fed back"positively" to the control circuit 7, that is, the sign of the gainP_(c) is negative in the formula (6). In other words, in the presentinvention ##EQU6## In this state, as is apparent from the formula (3),the spring constant of the parallel-plate springs 4-1 and 4-2 is verysmall, for example, as determined experimentally to be 0.1 g/mm.Therefore, if the stroke of the finger portions 3-1 and 3-2 is ±2 mm,the maximum generated force due to the position error is ±0.2 g.

Note that the damping coefficient and stiffness of the entire system aredetermined appropriately by using the formulas (4) and (5).

Thus, if a positive gripping force component is given as R(S), the robothand of FIG. 1 can grip the object 8 with a gripping force within anerror of ±0.2 g, regardless of the width of the object 8. Conversely, ifa negative gripping force is given as R(S), the finger portions 3-1 and3-2 are opened, and accordingly, the finger portion 3-2 comes in contactwith the stopper 9 with a definite force.

Also, in FIG. 1, it is possible to measure the width of the object 8 byusing the output signals of the strain gauges 5-1 and 5-2.

An example of the control circuit 6 of FIG. 1 is illustrated in FIG. 3.In FIG. 3, the output signals of the strain gauges 5-1 and 5-2 aresupplied to a buffer 31. The output signal of the buffer 31 is suppliedto a buffer 32 having the gain P_(c) and a differentiator 33 having thegain V_(c). Reference numeral 33 designates a resistor for detecting thecurrent flowing through the voice coil motor 7. The current detectingmeans formed by the resistor 34 has the gain I_(c). Reference numeral 35is an amplifier having the open-loop gain O_(c). The force informationsignal r{R(S)} and the output {X(S)} of the buffer 32 are appliedpositively to the amplifier 35, while the output {X(S)} of thedifferentiator 33 and the output {I(S)} of the resistor 34 are appliednegatively to the power amplifier 35. The output of the amplifier 35 isapplied to output transistors 36 and 37. That is, the power amplifier 35drives the voice coil motor 7 via the output transistors 36 and 37, sothat the sum of R(S)+X(S)-X(S) is zero.

In FIG. 2, the gains P_(c), V_(c), and I_(c) are manually adjusted;however, if the control circuit 6 is incorporated into a microcomputer,these gains P_(c), V_(c), and I_(c) can be adjusted by software.

In FIG. 1, since the voice coil motor 7 of a cylinder type is providedon the outside of the finger portion 3-2, the robot hand becomesrelatively large. Contrary to this, in FIG. 4, which is a modificationof the robot hand of FIG. 1, a voice coil motor 7' of a plate type isprovided on the side of the finger portions 3-1 and 3-2, therebyreducing the size of the robot hand. The voice coil motor 7' of a platetype is comprised of two yokes 71'-1 and 71'-2, permanent magnets 72'-1and 72'-2, a coil 73' of a plate type having terminals 73'a, a bobbin74', and a spacer 75' of a non-magnetic material. Reference numerals 10and 11 designate screw holes for assembling the voice coil motor 7'.

The yoke 71'-1 having the permanent magnet 72'-1 the spacer 75', and theyoke 71'-2 having the permanent magnet 72'-2 are mounted on the handbase 2 by inserting screws into screw holes 11. On the other hand, theplate type coil 73' associated with the bobbin 74' is mounted on thefinger portion 3-2 by inserting screws into the screw holes 10. Thus,when a current is supplied to the plate-type coil 73' via the terminals73'a, the current flowing through the coil 73' interacts with a magneticcircuit formed by the permanent magnets 72'-1 and 72'-2, thereby movingthe finger portion 3-2.

Note that such a voice coil motor 7' can be provided on both sides ofthe finger portions 3-1 and 3-2.

The bobbin 74' of FIG. 4 is conventionally made of plastic such as aresin. However, since plastic has a low heat conductivity, a plasticbobbin may be distorted by the heat generated by the coil 73'.Therefore, it is preferable that the bobbin 7' be made of aluminum,since aluminum has a high heat conductivity, a high shear modulus, and ahigh electrical conductivity. When an aluminum bobbin of a highelectrical conductivity moves within a magnetic field, a large eddycurrent is generated in the bobbin, thereby increasing the dampingcoefficient of the voice coil motor 7, which is helpful in stabilizingthe entire control system. In this case, it is necessary to completelyinsulate the coil 73' from the aluminum bobbin 74'. For this purpose,the alumimum bobbin 74' is preferably made by alumite processing,thereby obtaining a high insulation regardless of the number of turns ofthe coil 73'. Further, it is preferably that the aluminum bobbin 74' bemade by black alumite processing, thereby avoiding flaws in the coil73'. Still further, a groove having the same configuration as the coil73' is formed in the bobbin 74'.

Cobalt magnets having high magnetic susceptibility are used as thepermanent magnets 72'-1 and 72'-2, to reduce the size thereof. However,since a strong magnetic attraction or repulsion is generated betweensuch magnetized cobalt magnets, some problems occur when mounting themagnetized cobalt magnets on the yokes.

In order to easily mount the magnetized cobalt magnets 72'-1 and 72'-2on the yokes 71'-1 and 71'-2, respectively, a magnet fixing frame 76' ofnon-magnetic material is provided for each of the magnets 72'-1 and72'-2, as illustrated in FIG. 5. That is, apertures 76'a and 76'b areprovided in the magnet fixing frame 76', and accordingly, the mountingof the magnets 72'-2 (72'-1) is carried out by inserting the magnetsinto the apertures 76'a and 76'b. The thickness of the magnet fixingframe 76' is equal to or a little smaller than that of the magnets 72'-2(72'-1).

The robot hands as illustrated in FIGS. 1 through 5 can grip an objecthaving a small range of width depending upon the length of theparallel-plate type springs 4-1 and 4-2. For example, such a width rangeis about 4 mm. Therefore, exchange of the robot hands is carried out inaccordance with the magnitude of width of the objects.

In FIG. 6, which illustrates a second embodiment of the presentinvention, the finger portions 3-1 and 3-2 are provided at a feed screw61 which is divided into a left-handed screw portion and a right-handedscrew portion. For example, the finger portion 3-1 is provided at theleft-handed screw portion, while the finger portion 3-2 is provided atthe right-handed screw portion. Therefore, if the feed screw 61 rotatesin one direction, the finger portion 3-1 approaches the finger portion3-2, while, if the feed screw 61 rotates in the other direction, thefinger portion 3-1 separates from the finger portion 3-2. That is, thespan between the finger portions 3-1 and 3-2 is controlled by therotation of the feed screw 61 which is driven by a direct current (DC)motor 62. The DC motor 62 is connected to an angle encoder 63.

The finger portion 3-2 is also supported by the parallel-plate springs4-1 and 4-2 (see FIGS. 1 and 4) and is driven by the voice coil motor 7'which is the same as that of FIG. 4. Therefore, the voice coil motor 7'is controlled by the control circuit 6 which is the same as that of FIG.1.

As explained above, the span between the finger portions 3-1 and 3-2 isdriven by the DC motor 62. This DC motor 62 is controlled by anothercontrol circuit 64 which is comprised of a constant current amplifier641. That is, in the control circuit 64, a span information signal sp isapplied positively to the amplifier 641, while the output of the angleencoder 63 is applied negatively to the amplifier 641. Therefore, the DCmotor 62 is controlled by the negative feedback of the angle encoder 63to the DC motor 62, so that the output of the encoder 63 coincides withthe span information signal sp.

Thus, the voice coil motor 7' is used for the control of a grippingforce and the DC motor 62 is used for the control of the span betweenthe finger portions 3-1 and 3-2, thereby controlling a gripping forcefor an object regardless of the width thereof.

If a gripping force is controlled by only the DC motor with no voicecoil motor, it is almost impossible to control a very small grippingforce of the order of grams, since a blind band exists in a controlsystem due to the friction of the movable portions such as the feedscrew 61 and the DC motor 62. Of course, in the embodiment of FIG. 6, itis also impossible to contradict the span error due to theabove-mentioned blind band. However, with the present invention it ispossible to control a fine gripping force by driving the voice coilmotor where the span error is, for example, ±2 mm.

In other words, in the robot hand of FIG. 6, if the span informationsignal sp having an accuracy of ±2 mm is given to the control circuit64, it is possible to grip an object with a fine gripping force, sincethe voice coil motor 7' has no friction portion.

Note that the control circuits 6 and 64 can be also incorporated into amicrocomputer, so that the parameters such asγ, sp and the like arecontrolled by software.

In FIG. 6, the output of the displacement sensor (in this case, thestrain gauges) is fed back to the control circuit 6, thereby controllingthe voice coil motor 7', while the output of the angle encoder 63 is fedback to the control circuit 64, thereby controlling the DC motor 62.That is, the control for a gripping force is independent of the controlfor a span between the finger portions.

In FIG. 7, which illustrates a third embodiment of the presentinvention, there is illustrated a robot hand similar to the robot handof FIG. 6. However, the robot hand of FIG. 7 comprises no angle encoder.In FIG. 7, the output of the strain gauges (not shown) is appliedpositively to the control circuit 6, thereby controlling the voice coilmotor 7' which is the same as that of FIG. 4, and the output of thestrain gauges is also applied negatively to a control circuit 6',thereby controlling the DC motor 62 in a position control mode. That isthe output of the strain gauges is applied to both of the controlcircuits 6 and 6'.

In FIG. 8, which is a modification of the robot hand of FIG. 7, thevoice coil motor 7 of FIG. 1 is used instead of the voice coil motor 7'of FIG. 4. The robot hand of FIG. 8 has the same control means as thatof FIG. 7. Note that reference numeral 81 is a stopper.

In the robot hand of FIG. 7 (or FIG. 8), the voice coil motor 7' (or 7)mounted on the finger portion 3-2 is mainly operated, while the DC motor62 for rotating the feed screw 61 is additionally operated. That is,when it is impossible to grip an object by only the operation of thevoice coil motor 7' (or 7), the DC motor 62 is rotated so as to obtain apredetermined span between the finger portions 3-1 and 3-2.

Note that it is also impossible to control a small gripping force onlyby controlling the DC motor 62 in the same way as in the secondembodiment of FIG. 6.

The control block diagrams of the robot hand of FIG. 7 (or FIG. 8) areillustrated in FIG. 9 and 10. The control block diagram of FIG. 9 showsthe state where the finger portion 3-2 is not in contact with an object,while the control block diagram of FIG. 10 shows the state where thefinger portion 3-2 is in contact with the object.

That is, as is understood from FIGS. 9 and 10, in the embodiment of FIG.7, the output of the strain gauges 5-1 and 5-2 fixed to theparallel-plate springs 4-1 and 4-2 (see: FIG. 1) is fed back positivelyto the the control circuit 6 of voice coil motor 7', and simultaneously,the abovementioned output is fed back negatively to the control circuit6' of the DC motor 62. In other words, the feed control of the feedscrew 61 and the gripping force of the finger portions 3-1 and 3-2 areboth controlled by detecting the displacement of the parallel-platesprings 4-1 and 4-2.

Referring to FIG. 9, the difference voltage V(S) between the outputvoltage V₁ (S) of the power amplifier of the control circuit 6 and thecounterelectromotive force V₂ (S) is applied to the coil 73' (or 73) ofthe voice coil motor 7' (or 7). Therefore, the current I(S) flowingthrough the coil 73' (or 73) is given by ##EQU7## where L_(c) and R_(c)are the inductance and resistance of the voice coil motor 7' (or 7) andL_(c) S+R_(c) is the impedance of the voice coil motor 7' (or 7). Theforce F₁ (S) generated by the voice coil motor 7' (or 7), which isBlI(S) (Bl, I(S): force constant and current of the voice coil motor 7'(or 7)), is applied positively to the finger portion 3-2, while thereactive force F₂ (S) of the parallel-plate springs 4-1 and 4-2, whichis kX(S) (k: spring constant of the springs 4-1 and 4-2, X(S):displacement of the finger portion 3-2), is applied negatively to thefinger portion 3-2. Also, applied negatively to the finger portion 3-2is a force F₃ (S) given by

    F.sub.3 (S)=M.sub.c S.X'(S)

where M_(c) is the mass of the finger portion 3-2 and X'(S) is the speedof the feed screw 61. That is, the force F(S) (=F₁ (S)-F₂ (S)-F₃ (S)) isapplied to the finger portion 3-2. Therefore, the speed X(S) of thefinger portion 3-2 is given by ##EQU8##

Also, the displacement X(S) of the finger portion 3-2 is given byX(S)=X(S)/S.

The control circuit 6 of FIG. 9 has the same configuration as thecontrol circuit 6 of FIG. 2, except that the force information signal isgiven by U₂ (S).

On the other hand, the difference voltage V'(S) between the outputvoltage V₁ '(S) of the power amplifier of the control circuit 6' and thecounterelectromotive force V₂ '(S) is applied to the DC motor 62.Therefore, the current I'(S) flowing through the DC motor 62 is given by##EQU9## where L_(m) and R_(m) are the inductance and resistance of theDC motor 62 and L_(m) S+R_(m) is the impedance of the DC motor 62. Theforce F₁ '(S) generated by the DC motor 62, which is K_(m) I'(S) (K_(m),I'(S): induced voltage constant and current of the DC motor 62), isapplied positively to the feed screw 61, while the frictional forceF_(r) (S) of the DC motor 62, the feed screw 61, and the like is appliednegatively to the feed screw 61. Also, applied negatively to the feedscrew 61 is a force F₃ '(S) given by

    F.sub.3 (S)=M.sub.c SX'(S)

where M_(c) is the mass of the finger portion 3-2 and X(S) is thedisplacement speed of the finger portion 3-2. That is, the force F'(S)(=F₁ '(S)-F_(r) (S)-F₃ '(S)) is applied to the feed screw 61. Therefore,the speed X'(S) of the feed screw 61 is given by ##EQU10## where M_(m)is the mass obtained by subtracting the mass of the movable portion ofthe voice coil motor 7' (or 7) from the load mass of the DC motor 62.

Note that damping coefficients are omitted from the mechanical impedanceterms of FIGS. 9 and 10.

In the control circuit 6', P_(m), V_(m), and I_(m) are feedback gains ofthe displacement, the displacement speed, and current of the feed screw61, respectively. In addition, O_(m) is an open-loop gain of the poweramplifier of the control circuit 6'. Here, a span information signal U₁(S) (=O) is given to the power amplifier. An actual circuit of thecontrol circuit 6' can be constructed in the same manner as in FIG. 3,and accordingly, the details thereof are omitted.

In the state as illustrated in FIG. 9, the dynamic equations thereof areas follows. ##EQU11## Here, X_(c) is the displacement of the fingerportion 3-2; X_(m) is the displacement of the feed screw 61;

E_(c) is the voltage of the voice coil motor 7'

(or 7); and

E_(m) is the voltage of the DC motor 62.

In the state as illustrated in FIG. 9, the force information signal U₂(S) is given to the voice coil motor 7' (or 7), and the span informationsignal U₁ (S) (=O) is given to the DC motor 62. As a result, the voicecoil motor 7' (or 7) moves the finger portion 3-2 to a definite positiondefined by the stopper 81, and accordingly, x_(c) is generated in thedisplacement of the finger portion 3-2. Therefore, the DC motor 62 isoperated by the control circuit 6' so as to reduce the displacementx_(c) (X(S)) of the finger portion 3-2. In this case, however, even whenthe DC motor 62 is operated, the displacement x_(c) cannot be zero,unless the acceleration of the DC motor 62 is very large. Finally, thefinger portion 3-2 touches an object, and as a result, the dynamicequations (8), (9), (10), and (11) are changed as follows. ##EQU12##That is, if a timing when the finger portion 3-2 touches the object isan initial value (t=0), the control system is as illustrated in FIG. 10.Here, it is assumed that the open-loop gains O_(m) and O_(c) of thepower amplifiers are

    O.sub.m =O.sub.c =∞.

Then, the transfer function of the entire system is represented by##EQU13##

Since U₁ (S)=0, the input U₂ (S), the frictional force F_(r) (S), andthe output X(S) satisfy the following equation. ##EQU14## Thus, from theequation (16), it can be seen that: (i) the entire control system isobservable and controllable if ##EQU15## (ii) a steady-state positionerror is generated for a step input response; (iii) a steady-stateposition error is generated due to the frictional force; and

(iv) two actuators, i.e., the voice coil motor 7' (or 7) and the DCmotor 62 are controllable as one hybrid motor.

That is, since the characteristics as stated in (i) to (iv) are the sameas those of a system having only one DC motor, no improvement occurs forposition control. However, the gripping force F(S) for the fingerportion 3-2 is represented by ##EQU16## Therefore, if the displacementfeedback gain P_(c) is set by ##EQU17## and the displacement speedfeedback gain V_(c) is zero, then ##EQU18## That is, the gripping forceF(S) is controllable regardless of the displacement X(S), and is alsocontrollable without a time delay and a steady-state position error. Inother words, after the finger portion 3-2 touches the object, it ispossible to accurately control a fine gripping force regardless of thesteady-state position error of the DC motor 62.

Note that, even when the speed feedback gain V_(c) is zero, the dampingcoefficient of the entire system is not zero due to the dampingcoefficient D_(c), which is, however, very small, so that the system isstable.

In order to satisfy the equation (18), a linear relationship between thespring constant k of the parallel-plate springs 4-1 and 4-2 and theoutput of the displacement sensor is necessary. Since the parallel-platesprings 4-1 and 4-2 have a small shear modulus in one direction, andaccordingly, are not subjected to torsion, the strain gauges 5-1 and 5-2as the displacement sensor can accurately detect the spring constant kof the springs 4-1 and 4-2.

Thus, in the third embodiment, it is possible to accurately control aforce including a large force and a very small force, regardless ofexternal disturbances such as friction. Also, since an object is grippedunder the condition that the displacement of the springs is nearly zero,the feed screw 61 and the female screw portion of the finger portions3-1 and 3-2 do not rub together, thereby improving the endurancethereof.

As is apparent from the equations (16) and (18), the response speed ofthe robot hand of FIG. 7 (or FIG. 8) is dependent upon the positionfeedback gain P_(m) of the DC motor 62. The control system is generallyunstable, i.e., in an oscillating state when the gain P_(m) is large,however, such an oscillating state can be suppressed by the frictionalforce F_(r) (S). Therefore, in the third embodiment, since the grippingforce of the robot hand is not affected by the position error due to thefrictional force F_(r) (S), the frictional force F_(r) (S) can bemoderately large thereby increasing the response speed. In this regard,since a screw mechanism such as the feed screw 61 is used in the robothand of FIG. 7, the motion of the feed screw 61 generates a largefrictional force, thereby increasing the response speed.

FIGS. 11 through 15 illustrate a modification of the robot hand of FIG.7. In more detail, FIG. 12 is a side view of the robot hand of FIG. 11,and FIG. 13 is a cross-sectional view taken along the line A-A'. Also,FIGS. 14 and 15 correspond to FIGS. 11 and 12, respectively. That is, inFIGS. 11 and 12, the voice coil motor 7' is omitted, however, in FIGS.,14 and 15, the voice coil motor 7' is illustrated. As illustrated inFIGS. 11 and 14, a protrusion 1101 is provided outside of the fingerportion 3-2. Therefore, when the feed screw 61 is rotated so as to movethe finger portion 3-2 towards the outside, the protrusion 1101 is incontact with a side plate 1102 provided on a base 1103 of the robothand. Thus, the opening of the robot hand is also carried out by a forcecontrol mode. That is, in FIGS. 9 and 10, when a negative forceinformation signal is given as U₂ (S), the finger portion 3-2 is movedtoward the outside by the voice coil motor 7' (or 7), so that thedisplacement of the finger portion 3-2 is detected by the parallel-platesprings 4-1 and 4-2 and is transmitted to the control circuit 6' forcontrolling the DC motor 62. As a result, the DC motor 62 drives thefeed screw 61 to move the finger portion 3-2 towards the outside. Then,when the protrusion 1101 of the finger portion 3-2 is in contact withthe side plate 1102, the displacement of the finger portion 3-2 isrestored and the displacement of the springs 4-1 and 4-2 is restored,thereby stopping the DC motor 62.

In FIG. 16A, which is a modification of the finger portions 3-1 and 3-2of FIG. 7, finger portins 3-1' and 3-2' are shaped to grip an objectsuch as a cylindrical object 8' as illustrated in FIG. 16B. Whengripping such an object 8', a negative force information signal is givenas U₂ (S) in FIGS. 9 and 10. Note that other modifications are possiblefor the shape of the finger portions 3-1 and 3-2.

In FIG. 17, which is still another modification of the robot hand ofFIG. 7, the finger portions 3-1 and 3-2 are mounted on the feed screw 61by inserting the feed screw 61 into the female screw portions 171-1 and171-2 of the finger portions 3-1 and 3-2. In addition, the female screwportions 171-1 and 171-2 of the finger portions 3-1 and 3-2 arereinforced by nuts 172-1 and 172-2, respectively, and, in this case,elastic elements 173-1 and 173-2, which are made of, for example,rubber, are inserted therebetween. As a result, referring to FIG. 18which is in partial cross-section the elastic element 173-2 of FIG. 17,the elastic element 173-2 generates forces as indicated by the arrows,thereby avoiding backlash between the female portions 171-1 and 171-2 ofthe finger portions 3-1 and 3-2 and the feed screw 61. Such abacklashless structure is helpful in adjusting a predeterminedfrictional force F_(r) (S).

In FIG. 19, which is a fourth embodiment of the present invention, anangle encoder 63' and a control circuit 19 are added to the elements ofFIG. 7, in order to measure the width of a gripped object. Note that thecontrol circuits 6 and 6' are omitted from FIG. 19. The control circuit19 comprises an amplifier 191 for the displacement signal of the straingauges 5-1 and 5-2, an analog/digital (A/D) converter 192, a centralprocessing unit (CPU) 193, and a counter 194 for counting the outputsignal of the angle encoder 63'.

The operation of measuring the width of an object is carried out asfollows. First, a zero point is set, that is, the finger portions 3-1and 3-2 are closed with no object therebetween. At this time, thecounter 194 is cleared and the displacement signal of the strain gaugesis stored as an initial displacement value D₀ in the memory (not shown).Then, when actually gripping an object in the same manner as explainedabove, the CPU 193 fetches the displacement signal value D from thestrain gauges and the value C of the counter 194, and calculates thewidth W by

    W=C+α(D-D.sub.0)

where α is an experimentally determined constant. Thus, the width of anobject such as a soft object can be easily measured.

In FIG. 20, which is a fifth embodiment of the present invention, atactile apparatus is illustrated. FIG. 21 is also a cross-sectional viewof the tactile apparatus of FIG. 20, and FIG. 22 is an enlarged view ofthe voice coil motor portion of FIG. 21.

Referring to FIGS. 20, 21, and 22, reference numeral 101 designates acontact probe, 102 a voice coil motor, 103 two parallel-plate springs,104 a stopper, 105 a movable portion of a movable mechanism, 106 ahousing, 107 a robot arm, 108 a strain gauge, 109 a feed screw of themovable mechanism, 110 a nut portion of the movable mechanism, 111 and112 bearings, 113 a DC motor, 114 an angle encoder, 115 a stopper/guidefor the nut portion 110, and 116 a control circuit comprising twocontrol circuits 116, 1162 for controlling the voice coil motor 102 andthe DC motor 113, respectively, and a control circuit 1163 for measuringthe dimension.

Referring to FIG. 22, the voice coil motor 102 is comprised of a yoke1021, permanent magnets 1022 mounted on the yoke 1021, a movable portion1023, a coil 1024 wound on the movable portion 1023, and a stopper 1025for stopping the movable portion 1023.

The contact probe 101 is mounted on the movable portion 1023, andaccordingly, the contact probe 101 can come in contact with an object117 with a predetermined force. The movable portion 1023 of the voicecoil motor 102 is supported by the parallel plate springs 103.Therefore, the parallel-plate springs 103 are displaced by the force ofthe voice coil motor 102 and the reactive force of the contact strobe101. On the other hand, the yoke 1021 of the voice coil motor 102 ismounted on the movable portion 105 of the movable mechanism, and inaddition, the base of the parallel-plate springs 103 is mounted on themovable mechanism.

Referring to FIGS. 21 and 22, the strain gauge 108 is fixed to theparallel-plate springs 103. Therefore, when the parallel-plate springs103 are displaced, and a torsion is generated therein, the displacementof the springs 103 is detected by the strain gauge 108 which transmitsan output to the control circuit 116. The movable portion of the movablemechanism 105 is connected to the feed screw 109 at the nut portion 110thereof, and accordingly, the DC motor 113 drives the movable portion105 with a large stroke. The movable portion 105 is slidably connectedvia the linear bearing 111 to the stopper/guide 115 fixed to the housing106. The stopper/guide 115 stops the rotation of the nut portion 110.The rotational angle of the DC motor 113 detected by the angle encoder114 is in proportion to the motion amount of the movable portion 105driven by the feed screw 109.

In the same way as in the previously-mentioned embodiment, the voicecoil motor 102 has no frictional mechanism, while the movable mechanismincluding the DC motor 113, the feed screw 109 and the like isfrictional.

In FIG. 20, the control circuit 1161 receives the output signal of thestrain gauge 108 to control the voice coil motor 102, while the controlcircuit 1162 receives the output signal of the strain gauge 108 tocontrol the DC motor 113. That is, the control circuits 1161 and 1162correspond to the control circuits 6 and 6' of FIG. 7, respectively.Also, the control circuit 1163 is similar to the control circuit 19 ofFIG. 19.

The control system of the tactile apparatus of FIGS. 20, 21, and 21 isillustrated in FIG. 23 which is the same as FIG. 9, except that analogswitches SW1 and SW2 for switching operation modes are provided. Thedynamic system of the tactile apparatus of FIG. 23 shows the statewherein the contact probe 101 is not in contact with the object 117.When the contact probe 101 is in contact with the object 117, thedynamic system of the tactile apparatus is replaced by the dynamicsystem as shown in FIG. 10.

In FIG. 23, a motion indication signal U(S) is given to only the controlcircuit 1161. Also, the displacement X(S) of the voice coil motor 102 isfed back positively thereto, while the displacement X(S) of the voicecoil motor 102 is fed back negatively to the DC motor 113. That is, ifthe state of the analog switches SW1 and SW2 is as illustrated in FIG.23, the operation of the tactile apparatus of FIG. 20 is the same asthat of the robot hand of FIG. 7.

The method for measuring a three-dimensional shape will be explained

(1) Setting of the Initial Contact Pressure

The force due to the movable portion 1023 of the voice coil motor 102applied to the parallel-plate spring 103 is dependent upon the attitudeof the voice coil motor 102. Therefore, every time the attitude of thevoice coil motor 102 is changed, it is necessary to change the initialcontact pressure. That is, after the attitude of the contact probe 1 isset, the analog switches SW1 and SW2 are switched so that thedisplacement X(S) of the voice coil motor 102 is fed back negativelythereto, and the feedback amount of the displacement X(S) to the DCmotor 113 is zero. As a result, when the parallel-plate springs 103 areheld in a neutral state in which the current I(S) flowing through thecoil 1024 of the voice coil motor 102 generates a force in balance withthe weight of the voice coil motor 102, such a current I(S) is stored asthe initial contact pressure in the memory (not shown) by the controlcircuit 1163. Thus, the initial pressure value is added to a pressureindication value, thereby obtaining a predetermined contact pressure.

(2) Setting of the Initial Dimension

In this case, the analog switches SW1 and SW2 are switched to ameasuring mode. That is, the state of the analog switches SW1 and SW2 isthe same as illustrated in FIG. 23. As a result, the displacement X(S)of the voice coil motor 102 is fed back positively thereto, and thedisplacement X(S) of the voice coil motor 102 is applied positively tothe DC motor 113. When the control circuit 1163 detects that the housing106 is pressing on the stopper 104 at a definite pressure, the controlcircuit 1163 clears the counter (see FIG. 19) and stores thedisplacement of the voice coil motor 102 as the initial dimension in thememory.

(3) Measurement

After completion of the steps (1) and (2), it is possible to measure anobject unless the attitude of the voice coil motor 102 is changed. Thatis, the measured dimension is determined by the sum or difference of themotion amount of the feed screw 109 and the displacement of theparallel-plate springs 103.

According to the tactile apparatus as shown in FIGS. 20, 21, and 22, itis possible to support the contact probe 1 with a very small force ofthe order of grams. Also, since the set position of the contact probe isnot strictly fixed, it is easy to carry out an initial set, therebyenabling automation of the dimension measurements. Further, even if anobject is relatively soft, it is possible to measure the dimension ofthe object without damaging it.

The above-mentioned force generating apparatus, the gripping apparatus,or the tactile apparatus can be individually used and be incorporatedinto a robot system. Note that the force generating apparatuscorresponds to the gripping apparatus having only one finger portion,such as 3-2.

A robot system incorporating a force generating apparatus is illustratedin FIG. 24. In FIG. 24, reference numeral 201 designates a robot basehaving an X-axis driving motor, 202 an arm having a Z-axis drivingmotor, 203 an arm having a Y-axis driving motor, 204 a hand, 205 atwo-dimensional force generating apparatus having two kinds of voicecoil motors, and 206 a control circuit. The control circuit 206 iscomprised of an operation panel 2061, a memory 2062, a CPU 2063, a handposition control circuit 2064, a hand position circuit 2065, a drivercircuit 2066, and a hand control circuit 2067. During a position controlmode, the position control circuit 2064 receives position indicationsignals from the CPU 2063, thereby controlling the driver circuit 2066for driving the robot base 201 and the arms 202 and 203. However, duringa force control mode, the position indication signals from the CPU 2063regarding the X- and Y-axis are zero, so that the position controlcircuit 2064 controls the driver circuit 2066 by receiving thedisplacement X(S) and Y(S) of the voice coil motors included in theforce generating apparatus 205. In this case, the displacement X(S)regarding the X-axis is fed back positively to the voice coil motorregarding to the X-axis, however, the displacement X(S) is fed backnegatively to the X-axis driving motor. Similarly, the dieplacement Y(S)regarding the Y-axis is fed back positively to the voice coil motorregarding to the Y-axis, however, the displacement Y(S) is fed backnegatively to the Y-axis driving motor.

Referring to FIG. 25, which is a detailed diagram of the two-dimensionalforce generating apparatus of FIG. 24, reference numerals 2051 and 2052designate bases fixed to the arm 203 and the hand 206, respectively, 4Xand 4Y plate-type springs in the X- and Y-directions, respectively, 5Xand 5Y strain gauges in the X- and Y-directions, respectively, 72X and72Y permanent magnets, and 74X and &4Y coils in the X- and Y-directions,respectively. In this case, the permanent magnets 72X and the coil 74Xform an X-direction voice coil motor, and the permanent magnets 72Y andthe coil 74Y form a Y-direction voice coil motor.

In the embodiment of FIG. 24, a two-dimensional force generatingapparatus is used, however, it is possible to use a three-dimensionalforce generating appratus having three kinds of voice coil motors.

Further, when the tactile apparatus according to the present inventionis incorporated into a robot system, the absolute coordinates of anobject can be recognized easily by adding the coordinates of the robotarm to the value from the angle encoder of the DC motor of the tactileapparatus.

I claim:
 1. A force generating apparatus for applying a force to anobject by receiving a force information signal, comprising:a basemember; an elastic member fixed to said base member and producing areactive force when it is displaced; a movable member, fixed to saidelastic member, for applying said force corresponding to said forceinformation signal to said object; detecting means, provided on saidelastic member, for detecting the displacement thereof, so that saiddetecting means generates a displacement signal corresponding to thedisplacement; driving means for driving said movable member, comprisinga linear motor having a stator side fixed to said base member and amovable side fixed to said movable member; and control means, connectedto said detecting means and to said driving means for controlling saiddriving means by said force information signal to move said movablemember along a displacement direction, thereby applying a force to saidobject, and for controlling said driving means by said displacementsignal to move said movable member along said displacement direction,thereby counteracting said reactive force of said elastic member,wherein said reactive force is counteracted and said movable memberapplies only a force corresponding to said force information signal tosaid object.
 2. An apparatus as set forth in claim 1, wherein saidelastic member comprises leaf spring means.
 3. An apparatus as set forthin claim 1, wherein said elastic member comprises parallel-platesprings.
 4. An apparatus as set forth in claim 1, wherein said detectingmeans comprises strain gauge means.
 5. An apparatus as set forth inclaim 1, wherein said driving means comprises a moving coil motor.
 6. Anapparatus as set forth in claim 5, wherein said moving coil motorcomprises:a plate-type coil; and at least one plate-type permanentmagnet located in the vicinity of said plate-type coil.
 7. An apparatusas set forth in claim 6, wherein said permanent magnets are cobaltmagnets.
 8. An apparatus as set forth in claim 6, wherein said movingcoil motor further comprises a bobbin of aluminum.
 9. An apparatus asset forth in claim 8, wherein said bobbin of aluminum is made by alumiteprocessing.
 10. An apparatus as set forth in claim 6, wherein saidmoving coil motor further comprises at least one nonmagnetic platehaving a respective aperture for inserting each said plate-typepermanent magnet.
 11. An object processing system having a movablemechanism and receiving a predetermined force information signal,comprising:a force generating apparatus mounted on said movablemechanism, said force generating apparatus comprising: a base member; anelastic member attached to said base member and producing a reactiveforce when it is displaced; a movable member, attached to said elasticmember, applying a force corresponding to said force information signalto an object; first detecting means, provided on said elastic member,for detecting the displacement of said elastic member, so that saiddetecting means generates a displacement signal corresponding to thedisplacement; and first driving means for driving said movable member,comprising a linear motor having a stator side fixed to said base memberand a movable side fixed to said movable member; first control means,connected to said first detecting means and to said first driving means,for controlling said first driving means by said force informationsignal to move said movable member along a displacement direction,thereby applying a force to said object, and for controlling saiddriving means by said displacement signal to move said movable memberalong said displacement direction, counteracting said reactive force ofsaid elastic member and applying through said movable membersubstantially only the force corresponding to said force informationsignal to said object; means for applying said force information signalto said first control means; second driving means for driving saidmovable mechanism; and second control means, connected to said seconddriving means, for controlling said second driving means.
 12. A systemas set forth in claim 11, comprising:second detecting means, connectedto said second driving means, for detecting the displacement of saidmovable mechanism; wherein said second control means receives anexternally supplied position indication signal and a position detectingsignal from said second detecting means, and controls said seconddriving means so that said position detecting signal coincides with saidposition indication signal.
 13. A system as set forth in claim 11,wherein said second control means is connected to said first detectingmeans, and controls said second driving means by negative feedback ofthe displacement of said elastic member.
 14. A system as set forth inclaim 11, wherein said elastic member comprises leaf spring means.
 15. Asystem as set forth in claim 11, wherein said elastic member comprisesparallel-plate springs.
 16. A system as set forth in claim 11, whereinsaid first detecting means comprises strain gauge means.
 17. A system asset forth in claim 11, wherein said first driving means comprises amoving coil motor.
 18. A system as set forth in claim 11, wherein saidmoving coil motor comprises;a plate-type coil; and at least oneplate-type permanent magnet located in the vicinity of said plate-typecoil.
 19. A system as set forth in claim 18, wherein said permanentmagnets are cobalt magnets.
 20. A system as set forth in claim 18,wherein said moving coil motor further comprises a bobbin of aluminum.21. A system as set forth in claim 20, wherein said bobbin of aluminumis made by alumite processing.
 22. A system as set forth in claim 18,wherein said moving coil motor comprises at least one non-magnetic platehaving a respective aperture for inserting each said plate-type permentmagnet.
 23. A system as set forth in claim 11, wherein said movablemechanism comprises a feed screw on which said force generatingapparatus is mounted.
 24. A system as set forth in claim 23, whereinsaid movable mechanism comprises at least one nut, mounted on said feedscrew, for adjusting said force generating apparatus.
 25. A system asset forth in claim 24, wherein said movable mechanism comprises afurther elastic member inserted between said force generating apparatusand said nut.
 26. A system as set forth in claim 11, wherein said seconddriving means comprises a DC motor.
 27. A robot system including meansfor providing a force information signal, comprising:an arm; a forcegenerating apparatus mounted on the end of said arm, said forcegenerating apparatus comprising: a base member; an elastic memberattached to said base member; a movable member, attached to said elasticmember, applying a force corresponding to said force information signalto an object; first detecting means provided in said elastic member, fordetecting the displacement of said elastic member, so that said firstdetecting means generates a displacement signal corresponding to thedisplacement; and first driving means for driving said movable member,comprising a linear motor having a stator side fixed to said base memberand a movable side fixed to said movable member; first control means,connected to said detecting means and to said first driving means, forcontrolling said first driving means by said force information signal,to move said movable member along a displacement direction therebyapplying a force to said object, and for controlling said driving meansby said displacement signal to move said movable member along saiddisplacement direction, counteracting said reactive force counteractedand applying through said movable member substantially only a forcecorresponding to said force information signal to said object; seconddriving means for driving said arm; and second control means, connectedto said second driving means, for controlling said second driving means.28. A system as set forth in claim 27, comprising:second detectingmeans, connected to said second driving means, for detecting thedisplacement of said arm; wherein said second control means receives aposition indication signal and a position detecting signal from saidsecond detecting means, and controls said second driving means so thatsaid position detecting signal coincides with said position indicationsignal.
 29. A system as set forth in claim 27, wherein said secondcontrol means is connected to said first detecting means, and controlssaid second driving means by negative feedback of said displacement ofsaid elastic member.
 30. A system as set forth in claim 27, wherein saidelastic member comprises leaf spring means.
 31. A system as set forth inclaim 27, wherein said elastic member comprises parallel-plate springs.32. A system as set forth in claim 27, wherein said first detectingmeans comprises strain gauge means.
 33. A system as set forth in claim27, wherein said first driving means comprises a moving coil motor. 34.An apparatus as set forth in claim 33, wherein said moving coil motorcomprises:a plate-type coil; and at least one plate-type permanentmagnet located in the vicinity of said plate-type coil.
 35. A system asset forth in claim 34, wherein said permanent magnets are cobaltmagnets.
 36. A system as set forth in claim 34, wherein said moving coilmotor further comprises a bobbin of aluminum.
 37. A system as set forthin claim 36, wherein said bobbin of aluminum is made by alumiteprocessing.
 38. An apparatus as set forth in claim 27, wherein saidmoving coil motor further comprises a non-magnetic plate having arespective aperture for inserting each said plate-type permanent magnet.39. A system as set forth in claim 27, wherein said arm comprises a feedscrew on which said force generating apparatus is mounted.
 40. A systemas set forth in claim 39, wherein said arm further comprises a nut,mounted on said feed screw, for adjusting said force generatingapparatus.
 41. A system as set forth in claim 40, wherein said armcomprises a further elastic member inserted between said forcegenerating apparatus and said nut.
 42. A system as set forth in claim27, wherein said second driving means comprises a DC motor.
 43. A systemas set forth in claim 27, wherein said force generating apparatusgenerates forces in two dimensions.
 44. A system as set forth in claim27, wherein said force generating apparatus generates forces in threedimensions.
 45. A gripping apparatus for gripping an object, saidgripping apparatus comprising:two fingers for applying force to saidobject by gripping said object between said two fingers, at least one ofsaid two fingers including a base member, elastic member, movablemember, detecting means and driving means, said elastic member beingattached to said base member and producing a reactive force when it isdisplaced, said movable member being attached to said elastic member andapplying a force corresponding to said force information signal to saidobject, and said detecting means being provided in said elastic member,and for detecting the displacement of said elastic member, so that saiddetecting means generates a displacement signal corresponding to thedisplacement; and said driving means for driving said movable member,comprising a linear motor having a stator side fixed to said base memberand a movable side fixed to said movable member; and control means,connected to said detecting means and to said driving means, forcontrolling said driving means by said force information signal to movesaid movable member along a displacement direction thereby applying aforce to said object, and for controlling said driving means by saiddisplacement signal to move said movable member along said displacementdirection, counteracting said reactive force and applying through saidmovable member substantially only the force corresponding to said forceinformation signal to said object.
 46. An apparatus as set forth inclaim 45, wherein said elastic member comprises leaf spring means. 47.An apparatus as set forth in claim 45, wherein said elastic membercomprises parallel-plate springs.
 48. An apparatus as set forth in claim45, wherein said detecting means comprises strain gauge means.
 49. Anapparatus as set forth in claim 45, wherein said driving means comprisesa moving coil motor.
 50. An apparatus as set forth in claim 49, whereinsaid moving coil motor comprises:a plate-type coil; and at least oneplate-type permanent magnet located in the vicinity of said plate-typecoil.
 51. An apparatus as set forth in claim 50, wherein said permanentmagnets are cobalt magnets.
 52. An apparatus as set forth in claim 50,wherein said moving coil motor further comprises a bobbin of aluminum.53. An apparatus as set forth in claim 52, wherein said bobbin ofaluminum is made by alumite processing.
 54. An apparatus as set forth inclaim 50, wherein said moving coil motor further comprises anon-magnetic plate having a respective for inserting each saidplate-type permanent magnet.
 55. An object processing system,comprising:means for providing a force information signal; a movablemechanism having a gripping apparatus, including two fingers, mountedthereon, at least one of the two fingers including: a base member; anelastic member attached to said base member and producing a reactiveforce when it is displaced; a movable member, attached to said elasticmember, applying a force corresponding to said force information signalto an object; first detecting means, provided in said elastic member,for detecting the displacement of said elastic member so that said firstdetecting means generates a displacement signal corresponding to thedisplacement; and first driving means for driving said movable member,comprising a linear motor having a stator side fixed to said base memberand a movable side fixed to said movable member; first control means,connected to said first detecting means and to said first driving means,for controlling said first driving means by said force informationsignal to move said movable member along a displacement direction,thereby applying a force to said object, and for controlling saiddriving means by said displacement signal to move said movable memberalong said displacement direction, counteracting said reactive force andapplying through said movable member substantially only forcecorresponding to said force information signal to said object; seconddriving means for driving said movable mechanism; and second controlmeans, connected to said second driving means, for controlling saidsecond driving means.
 56. A system as set forth in claim 55, furthercomprising second detecting means, connected to said second drivingmeans, for detecting the displacement of said movable mechanism, saidsecond control means receiving an externally supplied positionindication signal and a position detecting signal from said seconddetecting means, and controlling said second driving means so that saidposition detecting signal coincides with said position indicationsignal.
 57. A system as set forth in claim 55, wherein said secondcontrol means is connected to said first detecting means, and controlssaid second driving means by negative feedback of the displacement ofsaid elastic member.
 58. A system as set forth in claim 55, wherein saidelastic member comprises leaf spring means.
 59. A system as set forth inclaim 55, wherein said elastic member comprises parallel-plate springs.60. A system as set forth in claim 55, wherein said first detectingmeans comprises strain gauge means.
 61. A system as set forth in claim55, wherein said first driving means comprises a moving coil motor. 62.A system as set forth in claim 61, wherein said moving coil motorcomprises:a plate-type coil; and at least one plate-type permanentmagnet located in the vicinity of said plate-type coil.
 63. A system asset forth in claim 62, wherein said permanent magnets are cobaltmagnets.
 64. A system as set forth in claim 62, wherein said moving coilmotor further comprises a bobbin of aluminum.
 65. A system as set forthin claim 64, wherein said bobbin of aluminum is made by alumiteprocessing.
 66. A system as set forth in claim 62, wherein said movingcoil motor further comprises non-magnetic plates having apertures forinserting said plate-type permanent magnets.
 67. A system as set forthin claim 55, wherein said movable mechanism comprises a feed screw onwhich said base member is mounted.
 68. A system as set forth in claim67, wherein said movable mechanism further comprises a nut, mounted onsaid feed screw, for adjusting said base member.
 69. A system as setforth in claim 68, wherein said movable mechanism comprises a furtherelastic member inserted between said base member and said nut.
 70. Asystem as set forth in claim 55, wherein said movable mechanismcomprises a feed screw having a left-hand screw portion and aright-handed screw portion, on one of which portions said base member ismounted, the other portion being mounted on the other finger.
 71. Asystem as set forth in claim 70, wherein said movable mechanism furthercomprises two nuts, mounted on said feed screw, for adjusting said basemember and the other finger.
 72. A system as set forth in claim 71,wherein said movable mechanism comprises tow further elastic membersinserted respectively between said base member and the other finger, andthe respective one of said nuts.
 73. A system as set forth in claim 55,wherein said second driving means comprises a DC motor.
 74. A robotsystem comprising: means for providing a force information signal; anarm having a gripping apparatus including two fingers, mounted thereon,at least one of the two fingers including:a base member; an elasticmember attached to said base member and producing a reactive force whenit is displaced; a movable member, attached to said elastic member,applying a force corresponding to an externally supplied forceinformation signal to an object; first detecting means, provided in saidelastic member, for detecting the displacement of said elastic member,so that said first detecting means generates a displacement signalcorresponding to the displacement; and first driving means for drivingsaid movable member, comprising a linear motor having a stator sidefixed to said base member and a movable side fixed to said movablemember; first control means, connected to said first detecting means andto said first driving means, for controlling said first driving means bysaid force information signal to move said movable member along adisplacement direction, thereby applying a force to said object, and forcontrolling said driving means by said displacement signal to move saidmovable member along said displacement direction, counteracting saidreactive force and applying through said movable member substantiallyonly said force corresponding to said force information signal to saidobject; second driving means for driving said movable mechanism; andsecond control means, connected to said second driving means, forcontrolling said second driving means.
 75. A system as set forth inclaim 74, further comprising:second detecting means, connected to saidsecond driving means, for detecting the displacement of said arm,wherein said second control means receives a position indication signaland a position detecting signal from said second detecting means, andcontrols said second driving means so that said position detectingsignal coincides with said position indication signal.
 76. A system asset forth in claim 74, wherein said second control means is connected tosaid first detecting means, and controls said second driving means bynegative feedback of said displacement of said elastic member.
 77. Asystem as set forth in claim 74, wherein said elastic member comprisesleaf spring means.
 78. A system as set forth in claim 74, wherein saidelastic member comprises parallel-plate springs.
 79. A system as setforth in claim 74, wherein said first detecting means comprises straingauge means.
 80. A system as set forth in claim 74, wherein said firstdriving means comprises a moving coil motor.
 81. A system as set forthin claim 80, wherein said moving coil motor comprises:a plate-type coil;and at least one plate-type permanent magnet located in the vicinity ofsaid plate-type coil.
 82. A system as set forth in claim 81, whereinsaid permanent magnets are cobalt magnets.
 83. A system as set forth inclaim 81, wherein said moving coil motor further comprises a bobbin ofaluminum.
 84. A system as set forth in claim 83, wherein said bobbin ofaluminum is made by alumite processing.
 85. A system as set forth inclaim 83, wherein said moving coil motor further comprises non-magneticplates having apertures for inserting said plate-type permanent magnets.86. A system as set forth in claim 74, wherein said arm comprises a feedscrew on which said base member is mounted.
 87. A system as set forth inclaim 86, wherein said arm comprises a nut, mounted on said feed screw,for adjusting said base member.
 88. A system as set forth in claim 87,wherein said arm comprises a further elastic member inserted betweensaid base member and said nut.
 89. A system as set forth in claim 74,wherein said arm comprises a feed screw having a left-hand screw portionand a right-hand screw portion, on one of which portions said basemember is mounted, the other finger being mounted on the other mountingportion.
 90. A system as set forth in claim 89, comprising two nuts,mounted on said feed screw, for adjusting said movable member and theother finger.
 91. A system as set forth in claim 90, wherein said armcomprises two further elastic members each inserted between a respectiveone of said base member and the other finger, and the respective one ofsaid nuts.
 92. A system as set forth in claim 74, wherein said seconddriving means comprises a DC motor.